Today I ventured out for a relatively short ride and experienced some very strange/scary fluctuations in my body temp in the middle of the ride. I wanted to see if anyone else has experienced this or might know what it was.

As a little context, this is my second season on my road bike, and I have about 1700 miles under my belt so far. I'm 28 and healthy.

I set out to do about 30-35 miles this afternoon under a relatively hot sun (heat index of 93 degrees). I started out pushing pretty hard because I have been feeling good lately (I finished back-to-back 75 mile rides two weekends ago, both in under 4 hrs; a couple days later did a fast 20-mile ride and two days after that a 13-mile sprint).

The first 10 miles were moderately hilly, and I averaged in the 21 mph range riding solo with a slight tailwind. As I hit the top of a hill at the 10-mile mark, I decided to take a short break. I drank some more water and ate half a powerbar. About 90 seconds in to my rest, I could feel my body temp falling, so I got back on the bike, fearing I was letting my heart rate fall too far.

However, I could not get back into any kind of rhythm or seem to get my speed back up over 18-19 mph. My legs didn't feel fried, but I did start feeling a bit nauseated - though not dizzy - and chilled. Before long I was getting goosebumps.

At this point I started getting concerned, so I headed home and took the rest of the ride pretty easy. Still, the goosebumps never really went away (AND I continued to sweat) and I didn't start to feel capable of pedaling hard again until the end of my ride (mile 19-20).

Any ideas?

My hypotheses so far:

-I just bonked (though why the drop in body temp?)
-I was not well hydrated/nourished enough going into the ride (i.e., I bonked)
-I rested too suddenly - without warming down - after being at a peak heart rate
-I was riding too high above my target heart rate for too long (wish I had a heart monitor!)